In the Armageddon TrilogyBarry has the power of time travel, however he appears to have lost this power when he appears in the other books. Indeed, there is a suggestion this may not be the same Barry. In Waiting For Godalming we discover at the end of the book that "Lazlo Woodbine" (owner of the head Barry is inhabiting) is actually suffering from delusions. Apart from this however, the first Barry (of Armageddon Trilogy fame) is a bio-engineered construct. In the other books he is a theopany - a gift from God's green garden. You see, everyone should have a guardian angel, but there simply aren't enough to go around, so everyone now has a holy guardian vegetable. Barry's main role as a Holy Guardian Sprout is to advise, and put up with his host. Barry often mumbles a snide comment if he's been badly treated, and this is often used to end a chapter or section of the book. Thusly:

Lazlo Woodbine has just outlined his plan to find God within twenty four hours and avert the wrath of Eartha, God's wife (Laz's latest client).
"You haven't got a hope, you feeble-minded sod"
"What was that, Barry?"
"I said put on your hat and coat and let's go and find God"